Diagnosing and Treating Snakebite in Horses and Livestock.
The danger/potency of a snakebite often depends on the amount of venom injected by the snake and the type of toxins in the venom, which can vary depending on species of snake. Most of the toxins affect muscles and blood vessels.
Rattlesnake venom contains a toxin that creates rapid swelling, pain and bleeding at the bite site and another toxin that damages blood vessels. The poison's damage is often relative to the size of the animal. A large animal like a horse or cow will often recover without complications from rattlesnake bites unless secondary infection develops. A dog, calf, foal, or child may experience severe snakebite symptoms and have serious complications. Rattlesnakes get rid of rats and other small rodents by immobilizing them with toxins. This causes them to die quickly, enabling the snake to eat them.
The toxins (and amounts of each) can differ in various bites and have different effects, but any bite can have serious complications if the bite becomes infected. Some of the worst cases are bites on the nose or face. Swelling may shut off air passages, making it difficult to breathe. The exertion of being herded or caught for treatment may make it even harder to breathe, and the increased heart rate from exertion may spread the poison.
It's usually easy to diagnose snakebite symptoms, especially on the face or muzzle. A snakebite on a foot or leg can make the animal lame, and lameness and swelling might be mistaken for foot rot or a badly strained/sprained joint or even a broken bone.
Cattle often recover without treatment and have more chance of survival than a horse when bitten on the nose or face since they can breathe through the mouth. Horses are more likely to suffocate. Swelling is the first snakebite symptom that will affect the animal. If you notice the bite when it is just starting to swell, you can insert a piece of hose or flexible tubing into each nostril.
Horses often get bitten on the nose because they are curious and approach the snake to smell it or see what it is. One veterinarian says the first thing he does when he goes on a call to see a horse that's been bitten on the nose is to try to open the airways with whatever he has. One time many years ago, he sent the farmer's wife to get her hair curlers--the pink foamy kind. He shoved the curlers up into the horse's nostrils to keep them open, and the horse survived.
If the swelling is too advanced and airways are already squeezed shut and the animal can't breathe, an emergency tracheostomy is necessary. It's best if this can be done by a veterinarian, but if a veterinarian can't get there on time and the animal is going to die, you can try to do it.
With a clean, sharp knife, make a vertical incision through the skin, along the windpipe, right in the middle of the throat--so you can get down to the cartilage rings of the trachea (similar to the ribs in a vacuum cleaner hose). Then use your fingers to open that slit a bit wider side-to-side so you can make a stab incision between the rings.
If that's not enough of a hole to let air go in and out, cut in a small circle, removing a portion of the cartilage ring to make a bigger hole. Often a pocketknife stab is enough between the rings to get it open for air flow. You can slip a small piece of hose or tube into the hole to keep it open. Having a snakebite first aid kit handy can buy some extra time until the veterinarian arrives.
A bite on the leg is usually not as serious, depending on where it is. The higher up the leg (near armpit or groin) the worse it might be. Toxins can then get into the bloodstream quicker, with more risk for anaphylactic shock. Toxins may also rupture red blood cells, and lead to organ failure, starting with the kidneys.
Usually what you see first is localized swelling from the bite. It may progress along the leg in the soft tissues. Your vet may have to surgically remove the dead tissue and get down to healthy tissue, and clean the wound.
Treatment for snakebite symptoms in horses and cattle is aimed at reducing the swelling and inflammation and may include anti-inflammatory drugs. Ice packs or cold packs can help reduce swelling and inflammation. Corticosteroids such as dexamethasone are often used, to decrease the risk for anaphylaxis (severe allergic reaction and shock). Nonsteroidal anti-inflammatory drugs like bute or Banamine are very beneficial for reducing swelling and inflammation.
Be aware that when you give a cow steroids in late pregnancy there is high risk for abortion. Corticosteroids don't seem to have the same effect on pregnant mares, and depending on the case, are often used on horses with snakebite symptoms.
DMSO (dimethyl sulfoxide) will also reduce the pain, swelling, and inflammation. DMSO gel or liquid can be rubbed over the area that's swelling. If the animal was bitten on the face, having trouble breathing, DMSO can also be given orally--mixed with a little warm water and squirted into the back of the mouth where it is rapidly absorbed and can keep the air passages open by halting tissue swelling. DMSO does a good job as an anti-oxidant and anti-inflammatory but it is also a penetrant and could take the toxin deeper into the tissue. Be careful how you use it.
The main goal in treating snakebite symptoms is to keep the toxin isolated and minimize spread. Confine the animal so it won't be moving around. Decreasing activity can slow down the spread of toxin by decreasing blood flow. A big dose of rattlesnake venom presents the risk of going systemic and causing organ failure after it gets into the bloodstream.
Antibiotics are often recommended, to minimize secondary bacterial infection from the affected area, especially if there's a lot of tissue damage. A bite with a lot of muscle toxin can cause necrosis in a large area. The secondary bacterial infection from a dirty bite (with a lot of necrotic tissue) may kill the animal, especially if you didn't find it early. If the animal is septic and ill, it will definitely need antibiotics.
Snakebites often become infected, and this can be more dangerous than the bite itself. There usually isn't enough poison in the venom to kill a large animal, but a serious infection may get started because of contamination from bacteria that enter with the bite; the dying tissue makes an ideal place for bacteria to multiply and send toxins into the bloodstream. If this type of infection (blood poisoning) is not treated promptly, the animal may die. Many veterinarians recommend broad-spectrum antibiotics until any possible infection is controlled. Tetanus antitoxin is also a good idea (especially for a horse or pet) if the animal's tetanus shots are not current. If the bite is several days old before discovered, there may be a large infected swelling that should be lanced and flushed.
If you should notice snakebite symptoms in your dog, there is a snakebite vaccine available for them. More recently a vaccine for horses became available that is intended to protect the horse throughout the summer from effects of rattlesnake venom. The dose is important; you want to achieve a high enough antibody level to protect the animal, based on its size. The smaller the animal, the more at risk it will be.
The recommendation when vaccinating horses is to start the first year with three doses (a few weeks apart) and then a booster every six months if you live in areas like parts of Texas and southern California where rattlesnakes are out year-round and never go dormant.
Owning a horse in northern areas where snakes are out for only a few months in summer, give a booster once a year--about a month before snakes start coming out. This gives horses enough time to ramp up immunity and be fully protected by the time they come into contact with rattlesnakes.
This vaccine was created specifically against venom from Western Diamondback rattlesnakes and is most effective against this snake's venom, but since venom from many other rattlesnakes is similar, this vaccine may also provide protection against venoms of the Prairie rattlesnake, Great Basic rattlesnake, Northern and Southern Pacific varieties, Sidewinder, Timber rattlesnake, Massasauga, and Copperhead. This vaccine does not provide much protection against venom from Water Moccasin (Cottonmouth), Mojave rattlesnake or Coral snake, however, since their venom is different.
Caption: Snakebitten cow.
Caption: ABOVE: Llama with tracheotomy, right: Llama after tracheotomy.
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|Title Annotation:||ANIMALS & LIVESTOCK :: SNAKEBITE|
|Author:||Thomas, Heather Smith|
|Publication:||Countryside & Small Stock Journal|
|Article Type:||Medical condition overview|
|Date:||Dec 22, 2017|
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